Mast block



FIG. 1 is a front view of the mast block showing the new design:

FIG. 2 is a back view thereof;

FIG. 3 is a left side view with thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a top perspective view thereof.

CLAIM I claim the ornamental design for a mast block, as shown anddescribed.